Predetermined Failure Mechanism in a Degradation System

ABSTRACT

In one aspect of the present invention, a degradation system comprises a driving mechanism. A holder assembly is connected to the driving mechanism. A pick is connected to both the driving mechanism and the holder assembly. At least one predetermined point of failure is configured in the holder assembly to dissipate the force on the pick when the tip of the pick is overloaded.

BACKGROUND OF THE INVENTION

The present invention relates generally to degradation machines, especially the type used to mill road structures. Degradation machines typically comprise a frame structure that supports a drum. Multiple holder assemblies, which support degradation picks, are attached to the drum. Man-holes or rail-road tracks are often buried underneath the surface of the road and will damage the picks if engaged at full speed. The prior art discloses mechanisms for protecting the picks.

U.S. Pat. No. 6,364,420 to Sollami, which is herein incorporated for all that it contains, discloses an improved means for providing for breakage of inexpensive replaceable parts when road resurfacing equipment and mining equipment bits encounter very hard irregularities in the surface being milled or mined.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the present invention, a degradation system comprises a driving mechanism. A holder assembly is connected to the driving mechanism. A pick is connected to both the driving mechanism and the holder assembly. In addition, at least one predetermined failure mechanism is configured to dissipate the force on the pick when a tip of the pick becomes overloaded.

A pick may comprise sintered polycrystalline diamond bonded to a cemented metal carbide substrate. A shank of the pick may be press fit into the holder assembly. The pick may comprise a front section that may rotate independent of the shank. The shank of the pick may rotate within the holder assembly.

The predetermined failure mechanism may comprise at least one shear pin that secures the holder assembly to the driving mechanism. The predetermined failure mechanism may also comprise at least one shear pin that attaches the pick to the holder assembly. The shear pin may fail when an extreme force is applied, this may result in preservation of the pick. The shank may be secured in a channel formed in the holder assembly; the channel may be deeper than the length of the pick's shank providing space for the pick to translate down into. In addition, the channel may provide protection for the pick from extreme applied forces.

The predetermined failure mechanism may comprise a discontinuous weld joint between the holder assembly and the driving mechanism that secures the holder assembly to the driving mechanism. The holder assembly may completely detach from the driving mechanism when the degradation system experiences detrimental forces.

A first portion of the holder assembly and/or driving mechanism may comprise a pivot pin that connects the holder assembly to the driving mechanism. A second portion of the holder assembly may be connected by a failure mechanism to the driving mechanism. A recess may be formed inside the driving mechanism proximate the holder assembly and the pivot. An inner face of the recess may comprise a magnet to restrain the holder assembly when pivoted inside the recess. An inner face of the recess may comprise a latch to restrain the holder assembly when pivoted inside the recess.

The degradation system may be a milling machine. The degradation system may be a downhole drilling string. The degradation system may be a trencher. The degradation system may be a mining machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an orthogonal diagram of an embodiment of a milling machine.

FIG. 2 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 3 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 4 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 5 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 6 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 7 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 8 is a cross sectional diagram of an embodiment of a holder assembly.

FIG. 9 is an orthogonal diagram of an embodiment of a trenching machine.

FIG. 10 is a cross sectional diagram of an embodiment of a drilling assembly.

FIG. 11 is a diagram of an embodiment of mining machine.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 discloses an embodiment of a degradation system. The degradation system may be a milling machine 100. Tracks 101 are used to move the machine along a desired direction of travel. A driving mechanism may be situated on the underside of the milling machine 100 and may comprise a rotary degradation drum 102. The rotary degradation drum 102 may comprise multiple holder assemblies 103. Each holder assembly 103 may contain one or more picks 104. Each individual pick 104 may comprise a tip enhanced with a sintered polycrystalline diamond bonded to a cemented metal carbide substrate.

The rotary degradation drum 102 may be rotated by diesel engine 105, electric engine, hydraulic mechanism, or combinations thereof. The engine 105 may be found at the forward end of the machine 100. As the rotary degradation drum 102 rotates, the picks 104 may engage the formation 106 and degrade it into aggregate.

FIG. 2 discloses a shank of a pick 104 secured within a channel 201 of a holder assembly 103. The holder assembly 103 is secured to the rotary degradation drum 102, which rotates in the direction of the arrow 200. The shank 202 is secured within the channel through both a press fit and a shear pin 203.

The tip of the pick 104 may rotate independent of the shank 202. A shear pin 203 may be incorporated into the assembly as part of a predetermined failure mechanism. The shear pin 203 may be engineered to withstand the forces inflicted during typical degradation processes. However, the shear pin 203 may be manufactured to absorb the impacts capable of breaking the pick's tip. To reduce the risk of damaging the tip, the shear pin 203 may break at forces lower than necessary to break the pick or its tip.

The formation 106 may at times comprise an unusually hard object, such as a buried manhole, pipe, railroad tie, etc. Such objects may not always be detected by the system operator and may cause irreversible damage. In this embodiment, the shear pin is loaded to a breaking point.

FIG. 3 discloses the shear pin after it breaks. The pick is pushed deeper into the channel 201. This backwards movement 300 provides the tip additional clearance to get around the manhole. At this point, the additional load on the picks may cause enough vibration through the milling machine that a sensor or operator realizes that the machine should be stopped. Thus, the shear pin, in this embodiment, buys the pick a little time before the drum is moved aware from the manhole. Preferably, the pick's integrity is preserved and may be reused by replacing the broken shear pin.

FIG. 4 discloses a top view of the pick. A shear pin 400 on the rearward side and a pivot pin 401 on the forward side may together connect the holder assembly to the rotary degradation drum 102. The shear pin may be manufactured to withstand forces resulting from degrading a formation only until a tip of the pick 104 becomes overloaded. While the pivot pin is not designed to break. The assembly may be positioned over a recess 402 cut into the surface of the drum 102.

FIG. 5 depicts the holder assembly 103, following the failure of the shear pin 400. With the drum moving in the direction of arrow 500 and the hard object in the road continuing to push on the pick in an opposing direction, the holder assembly 103 is pushed into the recess. The assembly may rotate about the pivot pin 401, which continues to secure the holder assembly 103 to the drum 102. Pushing the assembly into the recess provides clearance for the pick to get around the hard object. Preferably, the clearance is significant enough that the pick may rotate around the drum for several revolutions while still avoiding the hard object.

FIG. 6 discloses magnetic material 404 positioned in the recess 402 and configured to retain the holder inside the recess.

FIG. 7 discloses a collapsible latch 700 positioned inside the inner surface of the recess 402. The holder assembly 103 may pivot inside the recess 402, compressing the latch 700 in the process. A groove 701 may be cut into the exterior of the holder assembly 103. As the holder assembly 103 is pivoting into the recess 402, the latch 700 may become lodged inside the groove 701. The latch 700 may then expand inside the groove 701, fastening the pivoted holder assembly 103 into place inside the recess 402.

FIG. 8 discloses that two shear pins 400 may join the holder assembly 103 to the rotary degradation drum 102. The both shear pins 400 may be configured to fail upon engaging a hard formation 106. Thus, the entire assembly may be dislodged from the drum.

FIG. 9 discloses a trencher 1000 that comprises a plurality of picks on a rotating chain 1001. The rotating chain 1001 may be supported by an arm 1002 and may rotate down and into the formation 106 degrading it into aggregate. This process may form a trench while clearing the aggregate away into a conveyor belt that directs the aggregate to a side of the trench. The trencher 1000 may incorporate the present invention. The picks on the rotating chain 1001 may degrade a formation 106. The picks may comprise at least one predetermined failure mechanism configured to alleviate the force acting on the pick when a tip of the pick becomes overstrained.

FIG. 10 discloses an embodiment of a drill bit with a plurality of holder assemblies 103 attached to a downhole drill string 1100. Each holder assembly 103 may encase a pick 104 that may be press fit into a channel inside the assembly 103. The length of the channel inside the holder assembly 103 may extend further than the length of the pick's shank. Each of the pick's tips may comprise sintered polycrystalline diamond bonded to a cemented metal carbide substrate. A shear pin may be embedded between every holder assembly 103 and pick the assembly. The shear pin may be engineered to withstand degrading forces up to a predetermined quantity. This quantity is determined by the maximum magnitude of force that may need to be avoided to prevent potential harm from occurring to the picks 104.

FIG. 11 discloses a mining machine and/or coal excavator 1300 that incorporates the present invention. The cutting elements 1301 may be connected to the rotary degradation drum 102 that may be degrading the coal. The rotating drum 102 may be connected to an arm 1302 that moves the drum 102 vertically to allow engagement into the coal. The arm 1302 may move by a hydraulic arm. The arm 1302 may also pivot about an axis or a combination thereof. The coal excavator 1300 may move about by tracks, wheels, or a combination thereof. The coal excavator 1300 may also move about in a subterranean formation.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention. 

1. A degradation system, comprising: a holder assembly connected to the driving mechanism; a pick connected to the driving mechanism and the holder assembly; and at least one shear pin configured to dissipate the force on the pick when a tip of the pick is overloaded.
 2. The system of claim 1, wherein the tip comprises sintered polycrystalline diamond bonded to a cemented metal carbide substrate.
 3. The system of claim 1, wherein a shank of the pick is press fit into the holder assembly.
 4. The system of claim 1, wherein the pick comprises a front section that rotates independent of the shank.
 5. The system of claim 1, wherein a shank of the pick rotates within the holder assembly.
 6. The system of claim 1, wherein the shear pin secure the holder assembly to the driving mechanism.
 7. The system of claim 1, wherein the shear pin attaches the pick to the holder assembly.
 8. The system of claim 1, wherein the shank is secured in a channel formed in the holder assembly; the channel is deeper than the length of the pick's shank providing space for the pick to translate down into and providing protection for the pick from extreme applied forces.
 9. The system of claim 1, wherein the holder assembly completely detaches from the driving mechanism when the degradation system experiences detrimental forces.
 10. The system of claim 1, wherein a first portion of the holder assembly and/or driving mechanism comprises a pivot pin that connects the holder assembly to the driving mechanism.
 11. The system of claim 10, wherein a second portion of the holder assembly is connected by a failure mechanism to the driving mechanism. Rotation of the holder assembly may occur about the pivot pin and around the driving mechanism.
 12. The system of claim 11, wherein a recess is formed inside the driving mechanism proximate the holder assembly and the pivot.
 13. The system of claim 13, wherein an inner face of the recess comprises a magnet to restrain the holder assembly when pivoted inside the recess.
 14. The system of claim 13, wherein a face of the recess comprises a latch to restrain the holder assembly when pivoted inside the recess
 15. The system of claim 1, wherein the degradation system is a milling machine.
 16. The system of claim 1, wherein the degradation system is a downhole drilling string.
 17. The system of claim 1, wherein the degradation system is a trencher.
 18. The system of claim 1, wherein the degradation system is a mining machine. 